This invention relates to machine tools, and more particularly to a press of the type having an upper and a lower plate for chucking a set of tools consisting of an upper part and a lower part, one plate of which acts as the press ram, which is movable toward and away from the other plate acting as the press table, at least one T-slot being provided both in the chucking plates and in the upper and lower tool parts, and having at least two grippers mounted in each of either the upper chucking plate or in the upper tool part and in the lower chucking plate, with T-slots which are continuously aligned with the respective T-slot of the chucking plates or of the upper tool part, the T-slot of the upper chucking plate or the T-slot of the upper tool part having two recesses remote from one another.
The major part of the downtime for presses is caused by tool changes. Tools can weigh more than 500 kg without auxiliary plates. The changeover time for manual tool changes can be reduced by automatic hydraulic or hydromechanical tool chucking. Means such as the swivel grippers sold by the firm of Hilma GmbH, 5912 Hilchenbach, West Germany, are used for rapid chucking and dechucking of the tool on the press table or press ram. The tool has T-shaped recessed into which the tie rods of the swivel grippers are introduced by lowering the press-ram plate onto the upper tool part and are swivelled through 90.degree. in order to snap into the T-slots of the tool.
A great disadvantage of these swivel grippers is that if the pivoting mechanism of such grippers with tie rods becomes defective, the clamping connection can no longer be released because the chucking system is not accessible from behind the press. In such a case, the tool must be destroyed because there is no other way of removing it from the press.